Overlapped block motion compensation (obmc) blending selection in video coding

ABSTRACT

A device for decoding video data can be configured to determine that a block is coded in an overlapped block motion compensation (OBMC) mode; determine a first prediction block for the block using a first motion vector for the block; determine a second prediction block for the block using a second motion vector, wherein the second motion is a motion vector of a neighboring block of the block; select an OBMC blending process from a plurality of available OBMC blending processes; blend the first prediction block and the second prediction block using the selected OBMC blending process to determine a blended block; and reconstruct the block using the blended block.

This application claims the benefit of U.S. Provisional PatentApplication No. 63/268,789, filed 2 Mar. 2022, the entire contents ofwhich is incorporated herein by reference.

TECHNICAL FIELD

This disclosure relates to video encoding and video decoding.

BACKGROUND

Digital video capabilities can be incorporated into a wide range ofdevices, including digital televisions, digital direct broadcastsystems, wireless broadcast systems, personal digital assistants (PDAs),laptop or desktop computers, tablet computers, e-book readers, digitalcameras, digital recording devices, digital media players, video gamingdevices, video game consoles, cellular or satellite radio telephones,so-called “smart phones,” video teleconferencing devices, videostreaming devices, and the like. Digital video devices implement videocoding techniques, such as those described in the standards defined byMPEG-2, MPEG-4, ITU-T H.263, ITU-T H.264/MPEG-4, Part 10, Advanced VideoCoding (AVC), ITU-T H.265/High Efficiency Video Coding (HEVC), ITU-TH.266/Versatile Video Coding (VVC), and extensions of such standards, aswell as proprietary video codecs/formats such as AOMedia Video 1 (AV1)that was developed by the Alliance for Open Media. The video devices maytransmit, receive, encode, decode, and/or store digital videoinformation more efficiently by implementing such video codingtechniques.

Video coding techniques include spatial (intra-picture) predictionand/or temporal (inter-picture) prediction to reduce or removeredundancy inherent in video sequences. For block-based video coding, avideo slice (e.g., a video picture or a portion of a video picture) maybe partitioned into video blocks, which may also be referred to ascoding tree units (CTUs), coding units (CUs) and/or coding nodes. Videoblocks in an intra-coded (I) slice of a picture are encoded usingspatial prediction with respect to reference samples in neighboringblocks in the same picture. Video blocks in an inter-coded (P or B)slice of a picture may use spatial prediction with respect to referencesamples in neighboring blocks in the same picture or temporal predictionwith respect to reference samples in other reference pictures. Picturesmay be referred to as frames, and reference pictures may be referred toas reference frames.

SUMMARY

The techniques of this disclosure relate to inter prediction and, moreparticularly, to overlapped block motion compensation (OBMC), which is aprediction blending technique based on the current motion vectorinformation and the neighboring motion vector information. In OBMC, topredict a current block, a video decoder my locate a first referenceblock using a motion vector for the current block. The video decoder mayalso locate a second reference block using a motion vector of aneighboring block. The video decoder may then generate a predictionblock by blending the second reference block into the first referenceblock.

This disclosure describes techniques for using a comparison of atemplate matching cost between a template of the current block and atemplate of the first reference block with a template matching cost of atemplate of the current block and a template of the second referenceblock. Based on a comparison of the template matching costs, the videodecoder may select an OBMC blending process from a plurality ofavailable OBMC blending processes. The OBMC blending processes of theplurality of available OBMC blending processes may implement differentamounts of blending by utilizing different numbers of lines of thesecond reference block and different weightings. By selecting an OBMCblending process from a plurality of available OBMC blending processesin accordance with the techniques of this disclosure, a video decodermay achieve better prediction by varying, based on blockcharacteristics, the amount of blending performed in an OBMC operation.Moreover, by performing such selection based on a comparison of templatematching costs, the video decoder may achieve this better predictionwithout increasing signaling overhead.

According to an example of this disclosure, a method of decoding videodata includes determining that a block is coded in an overlapped blockmotion compensation (OBMC) mode; determining a first prediction blockfor the block using a first motion vector for the block; determining asecond prediction block for the block using a second motion vector,wherein the second motion is a motion vector of a neighboring block ofthe block; selecting an OBMC blending process from a plurality ofavailable OBMC blending processes; blending the first prediction blockand the second prediction block using the selected OBMC blending processto determine a blended block; and reconstructing the block using theblended block.

According to an example of this disclosure, a device for decodingencoded video data includes:

a memory configured to store video data and one or more processorsimplemented in circuitry and configured to determine that a block iscoded in an overlapped block motion compensation (OBMC) mode; determinea first prediction block for the block using a first motion vector forthe block; determine a second prediction block for the block using asecond motion vector, wherein the second motion is a motion vector of aneighboring block of the block; select an OBMC blending process from aplurality of available OBMC blending processes; blend the firstprediction block and the second prediction block using the selected OBMCblending process to determine a blended block; and reconstruct the blockusing the blended block.

According to an example of this disclosure, a computer-readable storagemedium stores instructions that when executed by one or more processorscause the one or more processors to determine that a block is coded inan overlapped block motion compensation (OBMC) mode; determine a firstprediction block for the block using a first motion vector for theblock; determine a second prediction block for the block using a secondmotion vector, wherein the second motion is a motion vector of aneighboring block of the block; select an OBMC blending process from aplurality of available OBMC blending processes; blend the firstprediction block and the second prediction block using the selected OBMCblending process to determine a blended block; and reconstruct the blockusing the blended block.

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description, drawings, and claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system that may perform the techniques of this disclosure.

FIGS. 2-4 show examples of overlapped block motion compensation (OBMC)blending in accordance with techniques of this disclosure.

FIG. 5 is a block diagram illustrating an example video encoder that mayperform the techniques of this disclosure.

FIG. 6 is a block diagram illustrating an example video decoder that mayperform the techniques of this disclosure.

FIG. 7 is a flowchart illustrating an example process for encoding acurrent block in accordance with the techniques of this disclosure.

FIG. 8 is a flowchart illustrating an example process for decoding acurrent block in accordance with the techniques of this disclosure.

FIG. 9 is a flowchart illustrating an example process for decoding acurrent block in accordance with the techniques of this disclosure.

DETAILED DESCRIPTION

Video coding (e.g., video encoding and/or video decoding) typicallyinvolves predicting a block of video data from either an already codedblock of video data in the same picture (e.g., intra prediction) or analready coded block of video data in a different picture (e.g., interprediction). In some instances, the video encoder also calculatesresidual data by comparing the prediction block to the original block.Thus, the residual data represents a difference between the predictionblock and the original block. To reduce the number of bits needed tosignal the residual data, the video encoder transforms and quantizes theresidual data and signals the transformed and quantized residual data inthe encoded bitstream. The compression achieved by the transform andquantization processes may be lossy, meaning that transform andquantization processes may introduce distortion into the decoded videodata.

A video decoder decodes and adds the residual data to the predictionblock to produce a reconstructed video block that matches the originalvideo block more closely than the prediction block alone. Due to theloss introduced by the transforming and quantizing of the residual data,the first reconstructed block may have distortion or artifacts. Onecommon type of artifact or distortion is referred to as blockiness,where the boundaries of the blocks used to code the video data arevisible.

To further improve the quality of decoded video, a video decoder canperform one or more filtering operations on the reconstructed videoblocks. Examples of these filtering operations include deblockingfiltering, sample adaptive offset (SAO) filtering, and adaptive loopfiltering (ALF). Parameters for these filtering operations may either bedetermined by a video encoder and explicitly signaled in the encodedvideo bitstream or may be implicitly determined by a video decoderwithout needing the parameters to be explicitly signaled in the encodedvideo bitstream.

The techniques of this disclosure relate to inter prediction and, moreparticularly, to overlapped block motion compensation (OBMC), which is aprediction blending technique based on the current MV information andthe neighboring MV information. Aspects of OBMC are described in M.Coban, F. L. Léannec, M. G. Sarwer, and J. Strom, “Algorithm descriptionof Enhanced Compression Model 3 (ECM 3),” JVET-X2025, January 2022. InOBMC, to predict a current block, a video decoder my locate a firstreference block using a motion vector for the current block. The videodecoder may also locate a second reference block using a motion vectorof a neighboring block. The video decoder may then generate a predictionblock by blending the second reference block into the first referenceblock.

This disclosure describes techniques for using a comparison of atemplate matching cost between a template of the current block and atemplate of the first reference block with a template matching cost of atemplate of the current block and a template of the second referenceblock. Based on a comparison of the template matching costs, the videodecoder may select an OBMC blending process from a plurality ofavailable OBMC blending processes. The OBMC blending processes of theplurality of available OBMC blending processes may implement differentamounts of blending by utilizing different numbers of lines of thesecond reference block and different weightings. By selecting an OBMCblending process from a plurality of available OBMC blending processesin accordance with the techniques of this disclosure, a video decodermay achieve better prediction by varying, based on blockcharacteristics, the amount of blending performed in an OBMC operation.Moreover, by performing such selection based on a comparison of templatematching costs, the video decoder may achieve this better predictionwithout increasing signaling overhead.

FIG. 1 is a block diagram illustrating an example video encoding anddecoding system 100 that may perform the techniques of this disclosure.The techniques of this disclosure are generally directed to coding(encoding and/or decoding) video data. In general, video data includesany data for processing a video. Thus, video data may include raw,unencoded video, encoded video, decoded (e.g., reconstructed) video, andvideo metadata, such as signaling data.

As shown in FIG. 1 , system 100 includes a source device 102 thatprovides encoded video data to be decoded and displayed by a destinationdevice 116, in this example. In particular, source device 102 providesthe video data to destination device 116 via a computer-readable medium110. Source device 102 and destination device 116 may comprise any of awide range of devices, including desktop computers, notebook (i.e.,laptop) computers, mobile devices, tablet computers, set-top boxes,telephone handsets such as smartphones, televisions, cameras, displaydevices, digital media players, video gaming consoles, video streamingdevice, broadcast receiver devices, or the like. In some cases, sourcedevice 102 and destination device 116 may be equipped for wirelesscommunication, and thus may be referred to as wireless communicationdevices.

In the example of FIG. 1 , source device 102 includes video source 104,memory 106, video encoder 200, and output interface 108. Destinationdevice 116 includes input interface 122, video decoder 300, memory 120,and display device 118. In accordance with this disclosure, videoencoder 200 of source device 102 and video decoder 300 of destinationdevice 116 may be configured to apply the techniques for OBMC. Thus,source device 102 represents an example of a video encoding device,while destination device 116 represents an example of a video decodingdevice. In other examples, a source device and a destination device mayinclude other components or arrangements. For example, source device 102may receive video data from an external video source, such as anexternal camera. Likewise, destination device 116 may interface with anexternal display device, rather than include an integrated displaydevice.

System 100 as shown in FIG. 1 is merely one example. In general, anydigital video encoding and/or decoding device may perform techniques forOBMC. Source device 102 and destination device 116 are merely examplesof such coding devices in which source device 102 generates coded videodata for transmission to destination device 116. This disclosure refersto a “coding” device as a device that performs coding (encoding and/ordecoding) of data. Thus, video encoder 200 and video decoder 300represent examples of coding devices, in particular, a video encoder anda video decoder, respectively. In some examples, source device 102 anddestination device 116 may operate in a substantially symmetrical mannersuch that each of source device 102 and destination device 116 includesvideo encoding and decoding components. Hence, system 100 may supportone-way or two-way video transmission between source device 102 anddestination device 116, e.g., for video streaming, video playback, videobroadcasting, or video telephony.

In general, video source 104 represents a source of video data (i.e.,raw, unencoded video data) and provides a sequential series of pictures(also referred to as “frames”) of the video data to video encoder 200,which encodes data for the pictures. Video source 104 of source device102 may include a video capture device, such as a video camera, a videoarchive containing previously captured raw video, and/or a video feedinterface to receive video from a video content provider. As a furtheralternative, video source 104 may generate computer graphics-based dataas the source video, or a combination of live video, archived video, andcomputer-generated video. In each case, video encoder 200 encodes thecaptured, pre-captured, or computer-generated video data. Video encoder200 may rearrange the pictures from the received order (sometimesreferred to as “display order”) into a coding order for coding. Videoencoder 200 may generate a bitstream including encoded video data.Source device 102 may then output the encoded video data via outputinterface 108 onto computer-readable medium 110 for reception and/orretrieval by, e.g., input interface 122 of destination device 116.

Memory 106 of source device 102 and memory 120 of destination device 116represent general purpose memories. In some examples, memories 106, 120may store raw video data, e.g., raw video from video source 104 and raw,decoded video data from video decoder 300. Additionally oralternatively, memories 106, 120 may store software instructionsexecutable by, e.g., video encoder 200 and video decoder 300,respectively. Although memory 106 and memory 120 are shown separatelyfrom video encoder 200 and video decoder 300 in this example, it shouldbe understood that video encoder 200 and video decoder 300 may alsoinclude internal memories for functionally similar or equivalentpurposes. Furthermore, memories 106, 120 may store encoded video data,e.g., output from video encoder 200 and input to video decoder 300. Insome examples, portions of memories 106, 120 may be allocated as one ormore video buffers, e.g., to store raw, decoded, and/or encoded videodata.

Computer-readable medium 110 may represent any type of medium or devicecapable of transporting the encoded video data from source device 102 todestination device 116. In one example, computer-readable medium 110represents a communication medium to enable source device 102 totransmit encoded video data directly to destination device 116 inreal-time, e.g., via a radio frequency network or computer-basednetwork. Output interface 108 may modulate a transmission signalincluding the encoded video data, and input interface 122 may demodulatethe received transmission signal, according to a communication standard,such as a wireless communication protocol. The communication medium maycomprise any wireless or wired communication medium, such as a radiofrequency (RF) spectrum or one or more physical transmission lines. Thecommunication medium may form part of a packet-based network, such as alocal area network, a wide-area network, or a global network such as theInternet. The communication medium may include routers, switches, basestations, or any other equipment that may be useful to facilitatecommunication from source device 102 to destination device 116.

In some examples, source device 102 may output encoded data from outputinterface 108 to storage device 112. Similarly, destination device 116may access encoded data from storage device 112 via input interface 122.Storage device 112 may include any of a variety of distributed orlocally accessed data storage media such as a hard drive, Blu-ray discs,DVDs, CD-ROMs, flash memory, volatile or non-volatile memory, or anyother suitable digital storage media for storing encoded video data.

In some examples, source device 102 may output encoded video data tofile server 114 or another intermediate storage device that may storethe encoded video data generated by source device 102. Destinationdevice 116 may access stored video data from file server 114 viastreaming or download.

File server 114 may be any type of server device capable of storingencoded video data and transmitting that encoded video data to thedestination device 116. File server 114 may represent a web server(e.g., for a web site), a server configured to provide a file transferprotocol service (such as File Transfer Protocol (FTP) or File Deliveryover Unidirectional Transport (FLUTE) protocol), a content deliverynetwork (CDN) device, a hypertext transfer protocol (HTTP) server, aMultimedia Broadcast Multicast Service (MBMS) or Enhanced MBMS (eMBMS)server, and/or a network attached storage (NAS) device. File server 114may, additionally or alternatively, implement one or more HTTP streamingprotocols, such as Dynamic Adaptive Streaming over HTTP (DASH), HTTPLive Streaming (HLS), Real Time Streaming Protocol (RTSP), HTTP DynamicStreaming, or the like.

Destination device 116 may access encoded video data from file server114 through any standard data connection, including an Internetconnection. This may include a wireless channel (e.g., a Wi-Ficonnection), a wired connection (e.g., digital subscriber line (DSL),cable modem, etc.), or a combination of both that is suitable foraccessing encoded video data stored on file server 114. Input interface122 may be configured to operate according to any one or more of thevarious protocols discussed above for retrieving or receiving media datafrom file server 114, or other such protocols for retrieving media data.

Output interface 108 and input interface 122 may represent wirelesstransmitters/receivers, modems, wired networking components (e.g.,Ethernet cards), wireless communication components that operateaccording to any of a variety of IEEE 802.11 standards, or otherphysical components. In examples where output interface 108 and inputinterface 122 comprise wireless components, output interface 108 andinput interface 122 may be configured to transfer data, such as encodedvideo data, according to a cellular communication standard, such as 4G,4G-LTE (Long-Term Evolution), LTE Advanced, 5G, or the like. In someexamples where output interface 108 comprises a wireless transmitter,output interface 108 and input interface 122 may be configured totransfer data, such as encoded video data, according to other wirelessstandards, such as an IEEE 802.11 specification, an IEEE 802.15specification (e.g., ZigBee™), a Bluetooth™ standard, or the like. Insome examples, source device 102 and/or destination device 116 mayinclude respective system-on-a-chip (SoC) devices. For example, sourcedevice 102 may include an SoC device to perform the functionalityattributed to video encoder 200 and/or output interface 108, anddestination device 116 may include an SoC device to perform thefunctionality attributed to video decoder 300 and/or input interface122.

The techniques of this disclosure may be applied to video coding insupport of any of a variety of multimedia applications, such asover-the-air television broadcasts, cable television transmissions,satellite television transmissions, Internet streaming videotransmissions, such as dynamic adaptive streaming over HTTP (DASH),digital video that is encoded onto a data storage medium, decoding ofdigital video stored on a data storage medium, or other applications.

Input interface 122 of destination device 116 receives an encoded videobitstream from computer-readable medium 110 (e.g., a communicationmedium, storage device 112, file server 114, or the like). The encodedvideo bitstream may include signaling information defined by videoencoder 200, which is also used by video decoder 300, such as syntaxelements having values that describe characteristics and/or processingof video blocks or other coded units (e.g., slices, pictures, groups ofpictures, sequences, or the like). Display device 118 displays decodedpictures of the decoded video data to a user. Display device 118 mayrepresent any of a variety of display devices such as a liquid crystaldisplay (LCD), a plasma display, an organic light emitting diode (OLED)display, or another type of display device.

Although not shown in FIG. 1 , in some examples, video encoder 200 andvideo decoder 300 may each be integrated with an audio encoder and/oraudio decoder, and may include appropriate MUX-DEMUX units, or otherhardware and/or software, to handle multiplexed streams including bothaudio and video in a common data stream.

Video encoder 200 and video decoder 300 each may be implemented as anyof a variety of suitable encoder and/or decoder circuitry, such as oneor more microprocessors, digital signal processors (DSPs), applicationspecific integrated circuits (ASICs), field programmable gate arrays(FPGAs), discrete logic, software, hardware, firmware or anycombinations thereof. When the techniques are implemented partially insoftware, a device may store instructions for the software in asuitable, non-transitory computer-readable medium and execute theinstructions in hardware using one or more processors to perform thetechniques of this disclosure. Each of video encoder 200 and videodecoder 300 may be included in one or more encoders or decoders, eitherof which may be integrated as part of a combined encoder/decoder (CODEC)in a respective device. A device including video encoder 200 and/orvideo decoder 300 may comprise an integrated circuit, a microprocessor,and/or a wireless communication device, such as a cellular telephone.

Video encoder 200 and video decoder 300 may operate according to a videocoding standard, such as ITU-T H.265, also referred to as HighEfficiency Video Coding (HEVC) or extensions thereto, such as themulti-view and/or scalable video coding extensions. Alternatively, videoencoder 200 and video decoder 300 may operate according to otherproprietary or industry standards, such as ITU-T H.266, also referred toas Versatile Video Coding (VVC). The VVC specification specifiesnormative bitstream and picture formats, high level syntax (HLS) andcoding unit level syntax, and the parsing and decoding process. VVC alsospecifies profiles/tiers/levels (PTL) restrictions, byte stream format,hypothetical reference decoder and supplemental enhancement information(SEI) in the annex.

In other examples, video encoder 200 and video decoder 300 may operateaccording to a proprietary video codec/format, such as AOMedia Video 1(AV1), extensions of AV1, and/or successor versions of AV1 (e.g., AV2).In other examples, video encoder 200 and video decoder 300 may operateaccording to other proprietary formats or industry standards. Thetechniques of this disclosure, however, are not limited to anyparticular coding standard or format. In general, video encoder 200 andvideo decoder 300 may be configured to perform the techniques of thisdisclosure in conjunction with any video coding techniques that useOBMC.

In general, video encoder 200 and video decoder 300 may performblock-based coding of pictures. The term “block” generally refers to astructure including data to be processed (e.g., encoded, decoded, orotherwise used in the encoding and/or decoding process). For example, ablock may include a two-dimensional matrix of samples of luminanceand/or chrominance data. In general, video encoder 200 and video decoder300 may code video data represented in a YUV (e.g., Y, Cb, Cr) format.That is, rather than coding red, green, and blue (RGB) data for samplesof a picture, video encoder 200 and video decoder 300 may code luminanceand chrominance components, where the chrominance components may includeboth red hue and blue hue chrominance components. In some examples,video encoder 200 converts received RGB formatted data to a YUVrepresentation prior to encoding, and video decoder 300 converts the YUVrepresentation to the RGB format. Alternatively, pre- andpost-processing units (not shown) may perform these conversions.

This disclosure may generally refer to coding (e.g., encoding anddecoding) of pictures to include the process of encoding or decodingdata of the picture. Similarly, this disclosure may refer to coding ofblocks of a picture to include the process of encoding or decoding datafor the blocks, e.g., prediction and/or residual coding. An encodedvideo bitstream generally includes a series of values for syntaxelements representative of coding decisions (e.g., coding modes) andpartitioning of pictures into blocks. Thus, references to coding apicture or a block should generally be understood as coding values forsyntax elements forming the picture or block.

HEVC defines various blocks, including coding units (CUs), predictionunits (PUs), and transform units (TUs). According to HEVC, a video coder(such as video encoder 200) partitions a coding tree unit (CTU) into CUsaccording to a quadtree structure. That is, the video coder partitionsCTUs and CUs into four equal, non-overlapping squares, and each node ofthe quadtree has either zero or four child nodes. Nodes without childnodes may be referred to as “leaf nodes,” and CUs of such leaf nodes mayinclude one or more PUs and/or one or more TUs. The video coder mayfurther partition PUs and TUs. For example, in HEVC, a residual quadtree(RQT) represents partitioning of TUs. In HEVC, PUs representinter-prediction data, while TUs represent residual data. CUs that areintra-predicted include intra-prediction information, such as anintra-mode indication.

As another example, video encoder 200 and video decoder 300 may beconfigured to operate according to VVC. According to VVC, a video coder(such as video encoder 200) partitions a picture into a plurality ofcoding tree units (CTUs). Video encoder 200 may partition a CTUaccording to a tree structure, such as a quadtree-binary tree (QTBT)structure or Multi-Type Tree (MTT) structure. The QTBT structure removesthe concepts of multiple partition types, such as the separation betweenCUs, PUs, and TUs of HEVC. A QTBT structure includes two levels: a firstlevel partitioned according to quadtree partitioning, and a second levelpartitioned according to binary tree partitioning. A root node of theQTBT structure corresponds to a CTU. Leaf nodes of the binary treescorrespond to coding units (CUs).

In an MTT partitioning structure, blocks may be partitioned using aquadtree (QT) partition, a binary tree (BT) partition, and one or moretypes of triple tree (TT) (also called ternary tree (TT)) partitions. Atriple or ternary tree partition is a partition where a block is splitinto three sub-blocks. In some examples, a triple or ternary treepartition divides a block into three sub-blocks without dividing theoriginal block through the center. The partitioning types in MTT (e.g.,QT, BT, and TT), may be symmetrical or asymmetrical.

When operating according to the AV1 codec, video encoder 200 and videodecoder 300 may be configured to code video data in blocks. In AV1, thelargest coding block that can be processed is called a superblock. InAV1, a superblock can be either 128×128 luma samples or 64×64 lumasamples. However, in successor video coding formats (e.g., AV2), asuperblock may be defined by different (e.g., larger) luma sample sizes.In some examples, a superblock is the top level of a block quadtree.Video encoder 200 may further partition a superblock into smaller codingblocks. Video encoder 200 may partition a superblock and other codingblocks into smaller blocks using square or non-square partitioning.Non-square blocks may include N/2×N, N×N/2, N/4×N, and N×N/4 blocks.Video encoder 200 and video decoder 300 may perform separate predictionand transform processes on each of the coding blocks.

AV1 also defines a tile of video data. A tile is a rectangular array ofsuperblocks that may be coded independently of other tiles. That is,video encoder 200 and video decoder 300 may encode and decode,respectively, coding blocks within a tile without using video data fromother tiles. However, video encoder 200 and video decoder 300 mayperform filtering across tile boundaries. Tiles may be uniform ornon-uniform in size. Tile-based coding may enable parallel processingand/or multi-threading for encoder and decoder implementations.

In some examples, video encoder 200 and video decoder 300 may use asingle QTBT or MTT structure to represent each of the luminance andchrominance components, while in other examples, video encoder 200 andvideo decoder 300 may use two or more QTBT or MTT structures, such asone QTBT/MTT structure for the luminance component and another QTBT/MTTstructure for both chrominance components (or two QTBT/MTT structuresfor respective chrominance components).

Video encoder 200 and video decoder 300 may be configured to usequadtree partitioning, QTBT partitioning, MTT partitioning, superblockpartitioning, or other partitioning structures.

In some examples, a CTU includes a coding tree block (CTB) of lumasamples, two corresponding CTBs of chroma samples of a picture that hasthree sample arrays, or a CTB of samples of a monochrome picture or apicture that is coded using three separate color planes and syntaxstructures used to code the samples. A CTB may be an N×N block ofsamples for some value of N such that the division of a component intoCTBs is a partitioning. A component is an array or single sample fromone of the three arrays (luma and two chroma) that compose a picture in4:2:0, 4:2:2, or 4:4:4 color format or the array or a single sample ofthe array that compose a picture in monochrome format. In some examples,a coding block is an M×N block of samples for some values of M and Nsuch that a division of a CTB into coding blocks is a partitioning.

The blocks (e.g., CTUs or CUs) may be grouped in various ways in apicture. As one example, a brick may refer to a rectangular region ofCTU rows within a particular tile in a picture. A tile may be arectangular region of CTUs within a particular tile column and aparticular tile row in a picture. A tile column refers to a rectangularregion of CTUs having a height equal to the height of the picture and awidth specified by syntax elements (e.g., such as in a picture parameterset). A tile row refers to a rectangular region of CTUs having a heightspecified by syntax elements (e.g., such as in a picture parameter set)and a width equal to the width of the picture.

In some examples, a tile may be partitioned into multiple bricks, eachof which may include one or more CTU rows within the tile. A tile thatis not partitioned into multiple bricks may also be referred to as abrick. However, a brick that is a true subset of a tile may not bereferred to as a tile. The bricks in a picture may also be arranged in aslice. A slice may be an integer number of bricks of a picture that maybe exclusively contained in a single network abstraction layer (NAL)unit. In some examples, a slice includes either a number of completetiles or only a consecutive sequence of complete bricks of one tile.

This disclosure may use “N×N” and “N by N” interchangeably to refer tothe sample dimensions of a block (such as a CU or other video block) interms of vertical and horizontal dimensions, e.g., 16×16 samples or 16by 16 samples. In general, a 16×16 CU will have 16 samples in a verticaldirection (y=16) and 16 samples in a horizontal direction (x=16).Likewise, an N×N CU generally has N samples in a vertical direction andN samples in a horizontal direction, where N represents a nonnegativeinteger value. The samples in a CU may be arranged in rows and columns.Moreover, CUs need not necessarily have the same number of samples inthe horizontal direction as in the vertical direction. For example, CUsmay comprise N×M samples, where M is not necessarily equal to N.

Video encoder 200 encodes video data for CUs representing predictionand/or residual information, and other information. The predictioninformation indicates how the CU is to be predicted in order to form aprediction block for the CU. The residual information generallyrepresents sample-by-sample differences between samples of the CU priorto encoding and the prediction block.

To predict a CU, video encoder 200 may generally form a prediction blockfor the CU through inter-prediction or intra-prediction.Inter-prediction generally refers to predicting the CU from data of apreviously coded picture, whereas intra-prediction generally refers topredicting the CU from previously coded data of the same picture. Toperform inter-prediction, video encoder 200 may generate the predictionblock using one or more motion vectors. Video encoder 200 may generallyperform a motion search to identify a reference block that closelymatches the CU, e.g., in terms of differences between the CU and thereference block. Video encoder 200 may calculate a difference metricusing a sum of absolute difference (SAD), sum of squared differences(SSD), mean absolute difference (MAD), mean squared differences (MSD),or other such difference calculations to determine whether a referenceblock closely matches the current CU. In some examples, video encoder200 may predict the current CU using uni-directional prediction orbi-directional prediction.

Some examples of VVC also provide an affine motion compensation mode,which may be considered an inter-prediction mode. In affine motioncompensation mode, video encoder 200 may determine two or more motionvectors that represent non-translational motion, such as zoom in or out,rotation, perspective motion, or other irregular motion types.

To perform intra-prediction, video encoder 200 may select anintra-prediction mode to generate the prediction block. Some examples ofVVC provide sixty-seven intra-prediction modes, including variousdirectional modes, as well as planar mode and DC mode. In general, videoencoder 200 selects an intra-prediction mode that describes neighboringsamples to a current block (e.g., a block of a CU) from which to predictsamples of the current block. Such samples may generally be above, aboveand to the left, or to the left of the current block in the same pictureas the current block, assuming video encoder 200 codes CTUs and CUs inraster scan order (left to right, top to bottom).

Video encoder 200 encodes data representing the prediction mode for acurrent block. For example, for inter-prediction modes, video encoder200 may encode data representing which of the various availableinter-prediction modes is used, as well as motion information for thecorresponding mode. For uni-directional or bi-directionalinter-prediction, for example, video encoder 200 may encode motionvectors using advanced motion vector prediction (AMVP) or merge mode.Video encoder 200 may use similar modes to encode motion vectors foraffine motion compensation mode.

AV1 includes two general techniques for encoding and decoding a codingblock of video data. The two general techniques are intra prediction(e.g., intra frame prediction or spatial prediction) and interprediction (e.g., inter frame prediction or temporal prediction). In thecontext of AV1, when predicting blocks of a current frame of video datausing an intra prediction mode, video encoder 200 and video decoder 300do not use video data from other frames of video data. For most intraprediction modes, video encoder 200 encodes blocks of a current framebased on the difference between sample values in the current block andpredicted values generated from reference samples in the same frame.Video encoder 200 determines predicted values generated from thereference samples based on the intra prediction mode.

Following prediction, such as intra-prediction or inter-prediction of ablock, video encoder 200 may calculate residual data for the block. Theresidual data, such as a residual block, represents sample by sampledifferences between the block and a prediction block for the block,formed using the corresponding prediction mode. Video encoder 200 mayapply one or more transforms to the residual block, to producetransformed data in a transform domain instead of the sample domain. Forexample, video encoder 200 may apply a discrete cosine transform (DCT),an integer transform, a wavelet transform, or a conceptually similartransform to residual video data. Additionally, video encoder 200 mayapply a secondary transform following the first transform, such as amode-dependent non-separable secondary transform (MDNSST), a signaldependent transform, a Karhunen-Loeve transform (KLT), or the like.Video encoder 200 produces transform coefficients following applicationof the one or more transforms.

As noted above, following any transforms to produce transformcoefficients, video encoder 200 may perform quantization of thetransform coefficients. Quantization generally refers to a process inwhich transform coefficients are quantized to possibly reduce the amountof data used to represent the transform coefficients, providing furthercompression. By performing the quantization process, video encoder 200may reduce the bit depth associated with some or all of the transformcoefficients. For example, video encoder 200 may round an n-bit valuedown to an m-bit value during quantization, where n is greater than m.In some examples, to perform quantization, video encoder 200 may performa bitwise right-shift of the value to be quantized.

Following quantization, video encoder 200 may scan the transformcoefficients, producing a one-dimensional vector from thetwo-dimensional matrix including the quantized transform coefficients.The scan may be designed to place higher energy (and therefore lowerfrequency) transform coefficients at the front of the vector and toplace lower energy (and therefore higher frequency) transformcoefficients at the back of the vector. In some examples, video encoder200 may utilize a predefined scan order to scan the quantized transformcoefficients to produce a serialized vector, and then entropy encode thequantized transform coefficients of the vector. In other examples, videoencoder 200 may perform an adaptive scan. After scanning the quantizedtransform coefficients to form the one-dimensional vector, video encoder200 may entropy encode the one-dimensional vector, e.g., according tocontext-adaptive binary arithmetic coding (CABAC). Video encoder 200 mayalso entropy encode values for syntax elements describing metadataassociated with the encoded video data for use by video decoder 300 indecoding the video data.

To perform CABAC, video encoder 200 may assign a context within acontext model to a symbol to be transmitted. The context may relate to,for example, whether neighboring values of the symbol are zero-valued ornot. The probability determination may be based on a context assigned tothe symbol.

Video encoder 200 may further generate syntax data, such as block-basedsyntax data, picture-based syntax data, and sequence-based syntax data,to video decoder 300, e.g., in a picture header, a block header, a sliceheader, or other syntax data, such as a sequence parameter set (SPS),picture parameter set (PPS), or video parameter set (VPS). Video decoder300 may likewise decode such syntax data to determine how to decodecorresponding video data.

In this manner, video encoder 200 may generate a bitstream includingencoded video data, e.g., syntax elements describing partitioning of apicture into blocks (e.g., CUs) and prediction and/or residualinformation for the blocks. Ultimately, video decoder 300 may receivethe bitstream and decode the encoded video data.

In general, video decoder 300 performs a reciprocal process to thatperformed by video encoder 200 to decode the encoded video data of thebitstream. For example, video decoder 300 may decode values for syntaxelements of the bitstream using CABAC in a manner substantially similarto, albeit reciprocal to, the CABAC encoding process of video encoder200. The syntax elements may define partitioning information forpartitioning of a picture into CTUs, and partitioning of each CTUaccording to a corresponding partition structure, such as a QTBTstructure, to define CUs of the CTU. The syntax elements may furtherdefine prediction and residual information for blocks (e.g., CUs) ofvideo data.

The residual information may be represented by, for example, quantizedtransform coefficients. Video decoder 300 may inverse quantize andinverse transform the quantized transform coefficients of a block toreproduce a residual block for the block. Video decoder 300 uses asignaled prediction mode (intra- or inter-prediction) and relatedprediction information (e.g., motion information for inter-prediction)to form a prediction block for the block. Video decoder 300 may thencombine the prediction block and the residual block (on asample-by-sample basis) to reproduce the original block. Video decoder300 may perform additional processing, such as performing a deblockingprocess to reduce visual artifacts along boundaries of the block.

This disclosure may generally refer to “signaling” certain information,such as syntax elements. The term “signaling” may generally refer to thecommunication of values for syntax elements and/or other data used todecode encoded video data. That is, video encoder 200 may signal valuesfor syntax elements in the bitstream. In general, signaling refers togenerating a value in the bitstream. As noted above, source device 102may transport the bitstream to destination device 116 substantially inreal time, or not in real time, such as might occur when storing syntaxelements to storage device 112 for later retrieval by destination device116.

Video encoder 200 and video decoder 300 may be configured to performOBMC. OBMC is a prediction blending process based on the current MVinformation and the neighboring MV information. There are two OBMCmodes, referred to as CU-Boundary OBMC mode and subblock-boundary OBMCmode.

FIG. 2 shows an example of CU-Boundary mode. When CU-boundary mode isused, the original prediction block (i.e., original block 130A andoriginal block 130B in FIG. 2 ) determined using the current CU MV andanother prediction block (i.e., block 132A and block 132B in FIG. 2 )determined using the neighboring CU MV are blended to form a blendedblock (i.e., block 134A and block 134B in FIG. 2 ). In the example ofFIG. 2 , block B_(T) represents a top neighboring block of block B₁, andblock B_(L) represents a left neighboring block of block B₂. Thus, videodecoder 300 locates prediction block 132A using the MV of block B_(T)and locates prediction block 132B using the MV for block B_(L).

As shown in FIG. 2 , a and b are weighting factors for the originalprediction derived by the current MV and the OBMC prediction derived bythe neighboring MV. The values of a and b depend on the distance to theCU boundary. For example, the values {13/16, 7/8, 15/16, 31/32} may beused for the value of “a” from a closest to a farthest distance to theboundary, and the values {3/16, 1/8, 1/16, 1/32} may be used for thevalue of “b” from a closest to a farthest distance to the boundary.

More specifically, video encoder 200 and video decoder 300 may beconfigured to perform the blending as follows:

-   -   Pixel1: The MC (motion compensation) result using current CU MV    -   Pixel2: The MC result using neighboring CU MV    -   NewPixel: The blended result from Pixel1 and Pixel2    -   For luma blocks, the number of blending pixel rows/columns is 4        and the corresponding weighting factors are:        -   1^(st) row or 1^(st) column (the row or column closest to            the CU boundary): NewPixel(i, j)=(26×Pixel1(i,            j)+6×Pixel2(i, j)+16)>>5        -   2^(nd) row or 2^(nd) column: NewPixel(i, j)=(7×Pixel1(i,            j)+Pixel2(i, j)+4)>>3        -   3^(rd) row or 3^(rd) column: NewPixel(i, j)=(15×Pixel1(i,            j)+Pixel2(i, j)+8)>>4        -   4^(th) row or 4^(th) column (the row or column farthest away            from the CU boundary): NewPixel(i, j)=(31×Pixel1(i,            j)+Pixel2(i, j)+16)>>5    -   For chroma blocks, the number of blending pixel rows/columns is        1 and the weighting factors are:        -   NewPixel(i, j)=(26×Pixel1(i, j)+6×Pixel2(i, j)+16)>>5

Subblock-boundary mode is enabled when a sub-CU coding tool is enabledfor a current CU, e.g. affine modes, SbTMVP, and subblock-basedbilateral matching. As shown in FIG. 3 , four separate OBMC blocks140A-140D using MVs of four connected neighboring sub-blocks 142A-142Bare blended with the original prediction block 144 using the currentsub-block MV. In ECM, CU-Boundary mode is performed beforeSubblock-Boundary mode. Generally, the blending is in 4×4 block basis.

The contribution “Non-EE2: Template Matching-based OBMC Design,”JVET-Y0076, 25th Meeting, by teleconference, 12-21 Jan. 2022, presents ablending selection technique to decide which blending process isselected according to the template matching costs. More specifically,three template matching costs (Cost1, Cost2, Cost3) are measured by SADbetween the reconstructed samples of a template and its correspondingreference samples of the reference template according to the motioninformation, where Cost1 is based on current motion information, Cost2us based on neighboring motion information, e.g. B_(T) or B_(L), andCost3 is based on weighted prediction of current motion information andneighboring motion information with weighting factors as ¾ and ¼respectively.

Video encoder 200 and video decoder 300 may then select a blendingprocess based on the costs as follows:

-   -   Pixel1: The MC result using current CU MV    -   Pixel2: The MC result using neighboring CU MV    -   If Cost1 is minimum: NewPixel(i, j)=Pixel1(i, j), i.e., no        blending.    -   If Cost2 is minimum: Same blending in ECM is used    -   If Cost3 is minimum: New blending is used        -   For luma blocks, 2 rows/columns are blended            -   1^(st) row or 1^(st) column (the row or column closest                to the CU boundary): NewPixel(i,                j)=(15×Pixel1(i,j)+Pixel2(i,j)+8)>>4            -   2^(nd) row or 2^(nd) column: NewPixel(i,                j)=(31×Pixel1(i,j)+Pixel2(i,j)+16)>>5        -   For chroma blocks, 1 row/column are blended            -   1^(st) row or 1^(st) column (the row or column closest                to the CU boundary): NewPixel(i,                j)=(15×Pixel1(i,j)+Pixel2(i,j)+8)>>4

Video encoder 200 and video decoder 300 may be configured to performblending filtering selection. According to the techniques of thisdisclosure, the blending process is decided based on the values of Cost1and Cost2, where Cost1 is the cost value derived by the current MVinformation used in the current CU, and Cost2 is the cost derived by theneighboring MV information, e.g. the MV information from B_(T) or B_(L).The blending processes can have different weighting factors and/ordifferent number of rows/columns for blending. Cost1 and Cost2 can bederived by the template matching, e.g., as described in JVET-Y0076. IfCost1>Cost2, no OBMC is used. Otherwise, Cost2>Cost1, then the blendingprocess 1 is used.

In one example, various blending processes are proposed and the bestblending process is decided based on the values of Cost1/Cost2 andCost2/Cost1. The value of Cost1/Cost2 can be decided into M categoriesby (M−1) pre-assigned positive thresholds, where M is non-negativeinteger, and is larger than or equal to 1. The value of Cost2/Cost1 canbe decided into N categories by (N−1) pre-assigned positive thresholds,where N is non-negative integer, and is larger than or equal to 1. M andN can be the same value or different values. Thresholds for Cost2/Cost1can be different from the thresholds for Cost1/Cost2. In anotherexample, Cost2/Cost1 and Cost1/Cost2 may share the same thresholds. Oneexample is there are four blending processes. M is 2 and N is 2, sothere is 1 threshold T1 for Cost2/Cost1 and another 1 threshold T2 forCost1/Cost2. Suppose Cost2/Cost1 and Cost1/Cost2 share the samethresholds, i.e., T=T1=T2. Then the blending process can be selected asfollows:

-   -   If Cost1*T≤Cost2: No OBMC.    -   Otherwise, if Cost1≤Cost2: blending 1 is used. One example is        15:1 for Col0/Row0, and 31:1 for Col1/Row1.    -   Otherwise, if Cost2*T≤Cost1: blending 2 is used. One example is        the current blending process in ECM, i.e., 26:6 for Col0/Row0,        7:1 for Col1/Row1, 15:1 for Col2/Row2, and 31:1 for Col3/Row3.    -   Otherwise, if Cost2<Cost1: blending 3 is used. One example is        7:1 for Col0/Row0, 15:1 for Col1/Row1, 31:1 for Col2/Row2.

By selecting no OBMC in response to Cost1*T≤Cost2, video decoder 300effectively uses only the first prediction block determined by themotion vector of the CU when a template matching cost between a templateof the CU and a template of the first prediction block is much less thana template matching cost between the template of the CU and a templateof the second prediction block determined by a motion vector of aneighboring CU. In contrast, if Cost2*T≤Cost1, then video decoder 300effectively performs more blending based on the second prediction blockin response to a template matching cost between the template of the CUand a template of the second prediction block being much less than atemplate matching cost between the template of the CU and a template ofthe first prediction block. In this regard, what constitutes “much less”may be controlled by the value of T.

In some examples, the thresholds are dependent on the CU sizes, thenumber of pixels in the CU, or the size of CU width or height. In otherword, there are Na thresholds for one threshold depending on the CUsizes, the number of pixels in the CU, or the size of CU width orheight. One example is there are four blending processes. M is 2 and Nis 2, so there is 1 threshold T1 for Cost2/Cost1 and another 1 thresholdT2 for Cost1/Cost2. Suppose Cost2/Cost1 and Cost1/Cost2 share the samethresholds, i.e., T=T1=T2. Suppose Na is set to be 3, which means thereare 3 thresholds for T. The different thresholds are set based on thenumber of pixels, denoted as Np, in the CU, such as T=Ta ifNp<preAssignedNum1, T=Tb if Np<preAssignedNum2, and otherwise T=Tc,where Ta<Tb<Tc are positive numbers, and preAssignedNum1<preAssignedNum2are positive integers (which should be smaller than or equal to thetotal number of pixels in current CU)

Video encoder 200 and video decoder 300 may be configured to performOBMC for an intra neighboring block. If B_(T) or B_(L) is intra codedblock, there is no MV information to generate the OBMC predictors toblend with the original subblock B₁ or B₂. According to the techniquesof this disclosure, video encoder 200 and/or video decoder 300 may beconfigured to reuse the MV information from one of the neighboringblocks (such as Ba, Bz of B_(T) in FIG. 4 ) of the intra coded blockB_(T) or B_(L) to generate the OBMC predictors 150A and 150B as shown inFIG. 4 .

In some examples, the maximum distance between Ba and B_(T) and themaximum distance between Bb and B_(T) may be smaller than a preassignedvalue D1, and also the maximum distance between Ba and B_(L) and themaximum distance between Bb and B_(L) may be smaller than a preassignedvalue D1. D1 is a positive value and may be a constant value. In oneexample, D1 can be dependent on the CU sizes so that D1 can be largerfor larger CU sizes and smaller for smaller CU sizes. One example isshown as follows: D1 is set to be 16 samples. Suppose the top-leftposition of B_(T) is (x, y). If B_(T) is intra coded block, then videoencoder 200 and video decoder 300 may check the neighboring blocks B_(T)in the following order: (x−4, y), (x+4, y), (x−8, y), (x+8, y), (x−12,y), (x+12, y), (x−16, y), (x+16, y). The first available MV informationis used to generate the OBMC predictors to blend with the originalsubblock B₁. The same can be applied to B_(L). D1 is set to be 16samples. Suppose the top-left position of B_(L) is (x, y). If B_(L) isintra coded block, then video encoder 200 and video decoder 300 maycheck the neighboring blocks B_(L) in the following order: (x, y−4), (x,y+4), (x, y−8), (x, y+8), (x, y−12), (x, y+12), (x, y+16), (x, y−16).

In some examples, the MV information (MVx, MVy) is used to generate theOBMC predictors only when the MV is similar to the current MV of B₁ orB₂, (MVOrgx, MVOrgy). In other words,|MVx−MVOrgx|<preAssignedMVDthreshold1,|MVy−MVOrgy|<preAssignedMVDthreshold2, where preAssignedMVDthreshold1and preAssignedMVDthreshold2 is a pre-defined positive values. In someexamples, preAssignedMVDthreshold1 and preAssignedMVDthreshold2 can bethe same value, and in some examples, preAssignedMVDthreshold1 andpreAssignedMVDthreshold2 can be different values. In some examples, notonly |MVx−MVOrgx|<preAssignedMVDthreshold1,|MVy−MVOrgy|<preAssignedMVDthreshold2 but the same reference pictureshould be satisfied when deciding which neighboring blocks are used togenerate the OBMC predictors.

FIG. 5 is a block diagram illustrating an example video encoder 200 thatmay perform the techniques of this disclosure. FIG. 5 is provided forpurposes of explanation and should not be considered limiting of thetechniques as broadly exemplified and described in this disclosure. Forpurposes of explanation, this disclosure describes video encoder 200according to the techniques of VVC (ITU-T H.266, under development), andHEVC (ITU-T H.265). However, the techniques of this disclosure may beperformed by video encoding devices that are configured to other videocoding standards and video coding formats, such as AV1 and successors tothe AV1 video coding format.

In the example of FIG. 5 , video encoder 200 includes video data memory230, mode selection unit 202, residual generation unit 204, transformprocessing unit 206, quantization unit 208, inverse quantization unit210, inverse transform processing unit 212, reconstruction unit 214,filter unit 216, decoded picture buffer (DPB) 218, and entropy encodingunit 220. Any or all of video data memory 230, mode selection unit 202,residual generation unit 204, transform processing unit 206,quantization unit 208, inverse quantization unit 210, inverse transformprocessing unit 212, reconstruction unit 214, filter unit 216, DPB 218,and entropy encoding unit 220 may be implemented in one or moreprocessors or in processing circuitry. For instance, the units of videoencoder 200 may be implemented as one or more circuits or logic elementsas part of hardware circuitry, or as part of a processor, ASIC, or FPGA.Moreover, video encoder 200 may include additional or alternativeprocessors or processing circuitry to perform these and other functions.

Video data memory 230 may store video data to be encoded by thecomponents of video encoder 200. Video encoder 200 may receive the videodata stored in video data memory 230 from, for example, video source 104(FIG. 1 ). DPB 218 may act as a reference picture memory that storesreference video data for use in prediction of subsequent video data byvideo encoder 200. Video data memory 230 and DPB 218 may be formed byany of a variety of memory devices, such as dynamic random access memory(DRAM), including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. Video datamemory 230 and DPB 218 may be provided by the same memory device orseparate memory devices. In various examples, video data memory 230 maybe on-chip with other components of video encoder 200, as illustrated,or off-chip relative to those components.

In this disclosure, reference to video data memory 230 should not beinterpreted as being limited to memory internal to video encoder 200,unless specifically described as such, or memory external to videoencoder 200, unless specifically described as such. Rather, reference tovideo data memory 230 should be understood as reference memory thatstores video data that video encoder 200 receives for encoding (e.g.,video data for a current block that is to be encoded). Memory 106 ofFIG. 1 may also provide temporary storage of outputs from the variousunits of video encoder 200.

The various units of FIG. 5 are illustrated to assist with understandingthe operations performed by video encoder 200. The units may beimplemented as fixed-function circuits, programmable circuits, or acombination thereof. Fixed-function circuits refer to circuits thatprovide particular functionality, and are preset on the operations thatcan be performed. Programmable circuits refer to circuits that can beprogrammed to perform various tasks, and provide flexible functionalityin the operations that can be performed. For instance, programmablecircuits may execute software or firmware that cause the programmablecircuits to operate in the manner defined by instructions of thesoftware or firmware. Fixed-function circuits may execute softwareinstructions (e.g., to receive parameters or output parameters), but thetypes of operations that the fixed-function circuits perform aregenerally immutable. In some examples, one or more of the units may bedistinct circuit blocks (fixed-function or programmable), and in someexamples, one or more of the units may be integrated circuits.

Video encoder 200 may include arithmetic logic units (ALUs), elementaryfunction units (EFUs), digital circuits, analog circuits, and/orprogrammable cores, formed from programmable circuits. In examples wherethe operations of video encoder 200 are performed using softwareexecuted by the programmable circuits, memory 106 (FIG. 1 ) may storethe instructions (e.g., object code) of the software that video encoder200 receives and executes, or another memory within video encoder 200(not shown) may store such instructions.

Video data memory 230 is configured to store received video data. Videoencoder 200 may retrieve a picture of the video data from video datamemory 230 and provide the video data to residual generation unit 204and mode selection unit 202. Video data in video data memory 230 may beraw video data that is to be encoded.

Mode selection unit 202 includes a motion estimation unit 222, a motioncompensation unit 224, and an intra-prediction unit 226. Mode selectionunit 202 may include additional functional units to perform videoprediction in accordance with other prediction modes. As examples, modeselection unit 202 may include a palette unit, an intra-block copy unit(which may be part of motion estimation unit 222 and/or motioncompensation unit 224), an affine unit, a linear model (LM) unit, or thelike.

Mode selection unit 202 generally coordinates multiple encoding passesto test combinations of encoding parameters and resultingrate-distortion values for such combinations. The encoding parametersmay include partitioning of CTUs into CUs, prediction modes for the CUs,transform types for residual data of the CUs, quantization parametersfor residual data of the CUs, and so on. Mode selection unit 202 mayultimately select the combination of encoding parameters havingrate-distortion values that are better than the other testedcombinations.

Video encoder 200 may partition a picture retrieved from video datamemory 230 into a series of CTUs, and encapsulate one or more CTUswithin a slice. Mode selection unit 202 may partition a CTU of thepicture in accordance with a tree structure, such as the MTT structure,QTBT structure. superblock structure, or the quad-tree structuredescribed above. As described above, video encoder 200 may form one ormore CUs from partitioning a CTU according to the tree structure. Such aCU may also be referred to generally as a “video block” or “block.”

In general, mode selection unit 202 also controls the components thereof(e.g., motion estimation unit 222, motion compensation unit 224, andintra-prediction unit 226) to generate a prediction block for a currentblock (e.g., a current CU, or in HEVC, the overlapping portion of a PUand a TU). For inter-prediction of a current block, motion estimationunit 222 may perform a motion search to identify one or more closelymatching reference blocks in one or more reference pictures (e.g., oneor more previously coded pictures stored in DPB 218). In particular,motion estimation unit 222 may calculate a value representative of howsimilar a potential reference block is to the current block, e.g.,according to sum of absolute difference (SAD), sum of squareddifferences (SSD), mean absolute difference (MAD), mean squareddifferences (MSD), or the like. Motion estimation unit 222 may generallyperform these calculations using sample-by-sample differences betweenthe current block and the reference block being considered. Motionestimation unit 222 may identify a reference block having a lowest valueresulting from these calculations, indicating a reference block thatmost closely matches the current block.

Motion estimation unit 222 may form one or more motion vectors (MVs)that defines the positions of the reference blocks in the referencepictures relative to the position of the current block in a currentpicture. Motion estimation unit 222 may then provide the motion vectorsto motion compensation unit 224. For example, for uni-directionalinter-prediction, motion estimation unit 222 may provide a single motionvector, whereas for bi-directional inter-prediction, motion estimationunit 222 may provide two motion vectors. Motion compensation unit 224may then generate a prediction block using the motion vectors. Forexample, motion compensation unit 224 may retrieve data of the referenceblock using the motion vector. As another example, if the motion vectorhas fractional sample precision, motion compensation unit 224 mayinterpolate values for the prediction block according to one or moreinterpolation filters. Moreover, for bi-directional inter-prediction,motion compensation unit 224 may retrieve data for two reference blocksidentified by respective motion vectors and combine the retrieved data,e.g., through sample-by-sample averaging or weighted averaging.

When operating according to the AV1 video coding format, motionestimation unit 222 and motion compensation unit 224 may be configuredto encode coding blocks of video data (e.g., both luma and chroma codingblocks) using translational motion compensation, affine motioncompensation, overlapped block motion compensation (OBMC), and/orcompound inter-intra prediction.

As another example, for intra-prediction, or intra-prediction coding,intra-prediction unit 226 may generate the prediction block from samplesneighboring the current block. For example, for directional modes,intra-prediction unit 226 may generally mathematically combine values ofneighboring samples and populate these calculated values in the defineddirection across the current block to produce the prediction block. Asanother example, for DC mode, intra-prediction unit 226 may calculate anaverage of the neighboring samples to the current block and generate theprediction block to include this resulting average for each sample ofthe prediction block.

When operating according to the AV1 video coding format,intra-prediction unit 226 may be configured to encode coding blocks ofvideo data (e.g., both luma and chroma coding blocks) using directionalintra prediction, non-directional intra prediction, recursive filterintra prediction, chroma-from-luma (CFL) prediction, intra block copy(IBC), and/or color palette mode. Mode selection unit 202 may includeadditional functional units to perform video prediction in accordancewith other prediction modes.

Mode selection unit 202 provides the prediction block to residualgeneration unit 204. Residual generation unit 204 receives a raw,unencoded version of the current block from video data memory 230 andthe prediction block from mode selection unit 202. Residual generationunit 204 calculates sample-by-sample differences between the currentblock and the prediction block. The resulting sample-by-sampledifferences define a residual block for the current block. In someexamples, residual generation unit 204 may also determine differencesbetween sample values in the residual block to generate a residual blockusing residual differential pulse code modulation (RDPCM). In someexamples, residual generation unit 204 may be formed using one or moresubtractor circuits that perform binary subtraction.

In examples where mode selection unit 202 partitions CUs into PUs, eachPU may be associated with a luma prediction unit and correspondingchroma prediction units. Video encoder 200 and video decoder 300 maysupport PUs having various sizes. As indicated above, the size of a CUmay refer to the size of the luma coding block of the CU and the size ofa PU may refer to the size of a luma prediction unit of the PU. Assumingthat the size of a particular CU is 2N×2N, video encoder 200 may supportPU sizes of 2N×2N or N×N for intra prediction, and symmetric PU sizes of2N×2N, 2N×N, N×2N, N×N, or similar for inter prediction. Video encoder200 and video decoder 300 may also support asymmetric partitioning forPU sizes of 2N×nU, 2N×nD, nL×2N, and nR×2N for inter prediction.

In examples where mode selection unit 202 does not further partition aCU into PUs, each CU may be associated with a luma coding block andcorresponding chroma coding blocks. As above, the size of a CU may referto the size of the luma coding block of the CU. The video encoder 200and video decoder 300 may support CU sizes of 2N×2N, 2N×N, or N×2N.

For other video coding techniques such as an intra-block copy modecoding, an affine-mode coding, and linear model (LM) mode coding, assome examples, mode selection unit 202, via respective units associatedwith the coding techniques, generates a prediction block for the currentblock being encoded. In some examples, such as palette mode coding, modeselection unit 202 may not generate a prediction block, and insteadgenerate syntax elements that indicate the manner in which toreconstruct the block based on a selected palette. In such modes, modeselection unit 202 may provide these syntax elements to entropy encodingunit 220 to be encoded.

As described above, residual generation unit 204 receives the video datafor the current block and the corresponding prediction block. Residualgeneration unit 204 then generates a residual block for the currentblock. To generate the residual block, residual generation unit 204calculates sample-by-sample differences between the prediction block andthe current block.

Transform processing unit 206 applies one or more transforms to theresidual block to generate a block of transform coefficients (referredto herein as a “transform coefficient block”). Transform processing unit206 may apply various transforms to a residual block to form thetransform coefficient block. For example, transform processing unit 206may apply a discrete cosine transform (DCT), a directional transform, aKarhunen-Loeve transform (KLT), or a conceptually similar transform to aresidual block. In some examples, transform processing unit 206 mayperform multiple transforms to a residual block, e.g., a primarytransform and a secondary transform, such as a rotational transform. Insome examples, transform processing unit 206 does not apply transformsto a residual block.

When operating according to AV1, transform processing unit 206 may applyone or more transforms to the residual block to generate a block oftransform coefficients (referred to herein as a “transform coefficientblock”). Transform processing unit 206 may apply various transforms to aresidual block to form the transform coefficient block. For example,transform processing unit 206 may apply a horizontal/vertical transformcombination that may include a discrete cosine transform (DCT), anasymmetric discrete sine transform (ADST), a flipped ADST (e.g., an ADSTin reverse order), and an identity transform (IDTX). When using anidentity transform, the transform is skipped in one of the vertical orhorizontal directions. In some examples, transform processing may beskipped.

Quantization unit 208 may quantize the transform coefficients in atransform coefficient block, to produce a quantized transformcoefficient block. Quantization unit 208 may quantize transformcoefficients of a transform coefficient block according to aquantization parameter (QP) value associated with the current block.Video encoder 200 (e.g., via mode selection unit 202) may adjust thedegree of quantization applied to the transform coefficient blocksassociated with the current block by adjusting the QP value associatedwith the CU. Quantization may introduce loss of information, and thus,quantized transform coefficients may have lower precision than theoriginal transform coefficients produced by transform processing unit206.

Inverse quantization unit 210 and inverse transform processing unit 212may apply inverse quantization and inverse transforms to a quantizedtransform coefficient block, respectively, to reconstruct a residualblock from the transform coefficient block. Reconstruction unit 214 mayproduce a reconstructed block corresponding to the current block (albeitpotentially with some degree of distortion) based on the reconstructedresidual block and a prediction block generated by mode selection unit202. For example, reconstruction unit 214 may add samples of thereconstructed residual block to corresponding samples from theprediction block generated by mode selection unit 202 to produce thereconstructed block.

Filter unit 216 may perform one or more filter operations onreconstructed blocks. For example, filter unit 216 may performdeblocking operations to reduce blockiness artifacts along edges of CUs.Operations of filter unit 216 may be skipped, in some examples.

When operating according to AV1, filter unit 216 may perform one or morefilter operations on reconstructed blocks. For example, filter unit 216may perform deblocking operations to reduce blockiness artifacts alongedges of CUs. In other examples, filter unit 216 may apply a constraineddirectional enhancement filter (CDEF), which may be applied afterdeblocking, and may include the application of non-separable,non-linear, low-pass directional filters based on estimated edgedirections. Filter unit 216 may also include a loop restoration filter,which is applied after CDEF, and may include a separable symmetricnormalized Wiener filter or a dual self-guided filter.

Video encoder 200 stores reconstructed blocks in DPB 218. For instance,in examples where operations of filter unit 216 are not performed,reconstruction unit 214 may store reconstructed blocks to DPB 218. Inexamples where operations of filter unit 216 are performed, filter unit216 may store the filtered reconstructed blocks to DPB 218. Motionestimation unit 222 and motion compensation unit 224 may retrieve areference picture from DPB 218, formed from the reconstructed (andpotentially filtered) blocks, to inter-predict blocks of subsequentlyencoded pictures. In addition, intra-prediction unit 226 may usereconstructed blocks in DPB 218 of a current picture to intra-predictother blocks in the current picture.

In general, entropy encoding unit 220 may entropy encode syntax elementsreceived from other functional components of video encoder 200. Forexample, entropy encoding unit 220 may entropy encode quantizedtransform coefficient blocks from quantization unit 208. As anotherexample, entropy encoding unit 220 may entropy encode prediction syntaxelements (e.g., motion information for inter-prediction or intra-modeinformation for intra-prediction) from mode selection unit 202. Entropyencoding unit 220 may perform one or more entropy encoding operations onthe syntax elements, which are another example of video data, togenerate entropy-encoded data. For example, entropy encoding unit 220may perform a context-adaptive variable length coding (CAVLC) operation,a CABAC operation, a variable-to-variable (V2V) length coding operation,a syntax-based context-adaptive binary arithmetic coding (SBAC)operation, a Probability Interval Partitioning Entropy (PIPE) codingoperation, an Exponential-Golomb encoding operation, or another type ofentropy encoding operation on the data. In some examples, entropyencoding unit 220 may operate in bypass mode where syntax elements arenot entropy encoded.

Video encoder 200 may output a bitstream that includes the entropyencoded syntax elements needed to reconstruct blocks of a slice orpicture. In particular, entropy encoding unit 220 may output thebitstream.

In accordance with AV1, entropy encoding unit 220 may be configured as asymbol-to-symbol adaptive multi-symbol arithmetic coder. A syntaxelement in AV1 includes an alphabet of N elements, and a context (e.g.,probability model) includes a set of N probabilities. Entropy encodingunit 220 may store the probabilities as n-bit (e.g., 15-bit) cumulativedistribution functions (CDFs). Entropy encoding unit 22 may performrecursive scaling, with an update factor based on the alphabet size, toupdate the contexts.

The operations described above are described with respect to a block.Such description should be understood as being operations for a lumacoding block and/or chroma coding blocks. As described above, in someexamples, the luma coding block and chroma coding blocks are luma andchroma components of a CU. In some examples, the luma coding block andthe chroma coding blocks are luma and chroma components of a PU.

In some examples, operations performed with respect to a luma codingblock need not be repeated for the chroma coding blocks. As one example,operations to identify a motion vector (MV) and reference picture for aluma coding block need not be repeated for identifying a MV andreference picture for the chroma blocks. Rather, the MV for the lumacoding block may be scaled to determine the MV for the chroma blocks,and the reference picture may be the same. As another example, theintra-prediction process may be the same for the luma coding block andthe chroma coding blocks.

Video encoder 200 represents an example of a device configured to encodevideo data including a memory configured to store video data, and one ormore processing units implemented in circuitry. As part of encodingvideo data, video encoder 200 may also perform video decoding todetermine how to encode video data and to generate reference pictures touse for coding subsequent pictures. Video encoder 200 may, for example,determine that a block is coded in an OBMC) mode, select an OBMCblending process from a plurality of available OBMC blending processes;and decode the block using the selected OBMC blending process.

FIG. 6 is a block diagram illustrating an example video decoder 300 thatmay perform the techniques of this disclosure. FIG. 6 is provided forpurposes of explanation and is not limiting on the techniques as broadlyexemplified and described in this disclosure. For purposes ofexplanation, this disclosure describes video decoder 300 according tothe techniques of VVC (ITU-T H.266, under development), and HEVC (ITU-TH.265). However, the techniques of this disclosure may be performed byvideo coding devices that are configured to other video codingstandards.

In the example of FIG. 6 , video decoder 300 includes coded picturebuffer (CPB) memory 320, entropy decoding unit 302, predictionprocessing unit 304, inverse quantization unit 306, inverse transformprocessing unit 308, reconstruction unit 310, filter unit 312, anddecoded picture buffer (DPB) 314. Any or all of CPB memory 320, entropydecoding unit 302, prediction processing unit 304, inverse quantizationunit 306, inverse transform processing unit 308, reconstruction unit310, filter unit 312, and DPB 314 may be implemented in one or moreprocessors or in processing circuitry. For instance, the units of videodecoder 300 may be implemented as one or more circuits or logic elementsas part of hardware circuitry, or as part of a processor, ASIC, or FPGA.Moreover, video decoder 300 may include additional or alternativeprocessors or processing circuitry to perform these and other functions.

Prediction processing unit 304 includes motion compensation unit 316 andintra-prediction unit 318. Prediction processing unit 304 may includeadditional units to perform prediction in accordance with otherprediction modes. As examples, prediction processing unit 304 mayinclude a palette unit, an intra-block copy unit (which may form part ofmotion compensation unit 316), an affine unit, a linear model (LM) unit,or the like. In other examples, video decoder 300 may include more,fewer, or different functional components.

When operating according to AV1, motion compensation unit 316 may beconfigured to decode coding blocks of video data (e.g., both luma andchroma coding blocks) using translational motion compensation, affinemotion compensation, OBMC, and/or compound inter-intra prediction, asdescribed above. Intra-prediction unit 318 may be configured to decodecoding blocks of video data (e.g., both luma and chroma coding blocks)using directional intra prediction, non-directional intra prediction,recursive filter intra prediction, CFL, intra block copy (IBC), and/orcolor palette mode, as described above.

CPB memory 320 may store video data, such as an encoded video bitstream,to be decoded by the components of video decoder 300. The video datastored in CPB memory 320 may be obtained, for example, fromcomputer-readable medium 110 (FIG. 1 ). CPB memory 320 may include a CPBthat stores encoded video data (e.g., syntax elements) from an encodedvideo bitstream. Also, CPB memory 320 may store video data other thansyntax elements of a coded picture, such as temporary data representingoutputs from the various units of video decoder 300. DPB 314 generallystores decoded pictures, which video decoder 300 may output and/or useas reference video data when decoding subsequent data or pictures of theencoded video bitstream. CPB memory 320 and DPB 314 may be formed by anyof a variety of memory devices, such as DRAM, including SDRAM, MRAM,RRAM, or other types of memory devices. CPB memory 320 and DPB 314 maybe provided by the same memory device or separate memory devices. Invarious examples, CPB memory 320 may be on-chip with other components ofvideo decoder 300, or off-chip relative to those components.

Additionally or alternatively, in some examples, video decoder 300 mayretrieve coded video data from memory 120 (FIG. 1 ). That is, memory 120may store data as discussed above with CPB memory 320. Likewise, memory120 may store instructions to be executed by video decoder 300, whensome or all of the functionality of video decoder 300 is implemented insoftware to be executed by processing circuitry of video decoder 300.

The various units shown in FIG. 6 are illustrated to assist withunderstanding the operations performed by video decoder 300. The unitsmay be implemented as fixed-function circuits, programmable circuits, ora combination thereof. Similar to FIG. 5 , fixed-function circuits referto circuits that provide particular functionality, and are preset on theoperations that can be performed. Programmable circuits refer tocircuits that can be programmed to perform various tasks, and provideflexible functionality in the operations that can be performed. Forinstance, programmable circuits may execute software or firmware thatcause the programmable circuits to operate in the manner defined byinstructions of the software or firmware. Fixed-function circuits mayexecute software instructions (e.g., to receive parameters or outputparameters), but the types of operations that the fixed-functioncircuits perform are generally immutable. In some examples, one or moreof the units may be distinct circuit blocks (fixed-function orprogrammable), and in some examples, one or more of the units may beintegrated circuits.

Video decoder 300 may include ALUs, EFUs, digital circuits, analogcircuits, and/or programmable cores formed from programmable circuits.In examples where the operations of video decoder 300 are performed bysoftware executing on the programmable circuits, on-chip or off-chipmemory may store instructions (e.g., object code) of the software thatvideo decoder 300 receives and executes.

Entropy decoding unit 302 may receive encoded video data from the CPBand entropy decode the video data to reproduce syntax elements.Prediction processing unit 304, inverse quantization unit 306, inversetransform processing unit 308, reconstruction unit 310, and filter unit312 may generate decoded video data based on the syntax elementsextracted from the bitstream.

In general, video decoder 300 reconstructs a picture on a block-by-blockbasis. Video decoder 300 may perform a reconstruction operation on eachblock individually (where the block currently being reconstructed, i.e.,decoded, may be referred to as a “current block”).

Entropy decoding unit 302 may entropy decode syntax elements definingquantized transform coefficients of a quantized transform coefficientblock, as well as transform information, such as a quantizationparameter (QP) and/or transform mode indication(s). Inverse quantizationunit 306 may use the QP associated with the quantized transformcoefficient block to determine a degree of quantization and, likewise, adegree of inverse quantization for inverse quantization unit 306 toapply. Inverse quantization unit 306 may, for example, perform a bitwiseleft-shift operation to inverse quantize the quantized transformcoefficients. Inverse quantization unit 306 may thereby form a transformcoefficient block including transform coefficients.

After inverse quantization unit 306 forms the transform coefficientblock, inverse transform processing unit 308 may apply one or moreinverse transforms to the transform coefficient block to generate aresidual block associated with the current block. For example, inversetransform processing unit 308 may apply an inverse DCT, an inverseinteger transform, an inverse Karhunen-Loeve transform (KLT), an inverserotational transform, an inverse directional transform, or anotherinverse transform to the transform coefficient block.

Furthermore, prediction processing unit 304 generates a prediction blockaccording to prediction information syntax elements that were entropydecoded by entropy decoding unit 302. For example, if the predictioninformation syntax elements indicate that the current block isinter-predicted, motion compensation unit 316 may generate theprediction block. In this case, the prediction information syntaxelements may indicate a reference picture in DPB 314 from which toretrieve a reference block, as well as a motion vector identifying alocation of the reference block in the reference picture relative to thelocation of the current block in the current picture. Motioncompensation unit 316 may generally perform the inter-prediction processin a manner that is substantially similar to that described with respectto motion compensation unit 224 (FIG. 5 ).

As another example, if the prediction information syntax elementsindicate that the current block is intra-predicted, intra-predictionunit 318 may generate the prediction block according to anintra-prediction mode indicated by the prediction information syntaxelements. Again, intra-prediction unit 318 may generally perform theintra-prediction process in a manner that is substantially similar tothat described with respect to intra-prediction unit 226 (FIG. 5 ).Intra-prediction unit 318 may retrieve data of neighboring samples tothe current block from DPB 314.

Reconstruction unit 310 may reconstruct the current block using theprediction block and the residual block. For example, reconstructionunit 310 may add samples of the residual block to corresponding samplesof the prediction block to reconstruct the current block.

Filter unit 312 may perform one or more filter operations onreconstructed blocks. For example, filter unit 312 may performdeblocking operations to reduce blockiness artifacts along edges of thereconstructed blocks. Operations of filter unit 312 are not necessarilyperformed in all examples.

Video decoder 300 may store the reconstructed blocks in DPB 314. Forinstance, in examples where operations of filter unit 312 are notperformed, reconstruction unit 310 may store reconstructed blocks to DPB314. In examples where operations of filter unit 312 are performed,filter unit 312 may store the filtered reconstructed blocks to DPB 314.As discussed above, DPB 314 may provide reference information, such assamples of a current picture for intra-prediction and previously decodedpictures for subsequent motion compensation, to prediction processingunit 304. Moreover, video decoder 300 may output decoded pictures (e.g.,decoded video) from DPB 314 for subsequent presentation on a displaydevice, such as display device 118 of FIG. 1 .

In this manner, video decoder 300 represents an example of a videodecoding device including a memory configured to store video data, andone or more processing units implemented in circuitry and configured todetermine that a block is coded in an OBMC) mode, select an OBMCblending process from a plurality of available OBMC blending processes;and decode the block using the selected OBMC blending process.

FIG. 7 is a flowchart illustrating an example process for encoding acurrent block in accordance with the techniques of this disclosure. Thecurrent block may comprise a current CU. Although described with respectto video encoder 200 (FIGS. 1 and 2 ), it should be understood thatother devices may be configured to perform a process similar to that ofFIG. 7 .

In this example, video encoder 200 initially predicts the current block(350). For example, video encoder 200 may form a prediction block forthe current block. Video encoder 200 may then calculate a residual blockfor the current block (352). To calculate the residual block, videoencoder 200 may calculate a difference between the original, unencodedblock and the prediction block for the current block. Video encoder 200may then transform the residual block and quantize transformcoefficients of the residual block (354). Next, video encoder 200 mayscan the quantized transform coefficients of the residual block (356).During the scan, or following the scan, video encoder 200 may entropyencode the transform coefficients (358). For example, video encoder 200may encode the transform coefficients using CAVLC or CABAC. Videoencoder 200 may then output the entropy encoded data of the block (360).

FIG. 8 is a flowchart illustrating an example process for decoding acurrent block of video data in accordance with the techniques of thisdisclosure. The current block may comprise a current CU. Althoughdescribed with respect to video decoder 300 (FIGS. 1 and 3 ), it shouldbe understood that other devices may be configured to perform a processsimilar to that of FIG. 8 .

Video decoder 300 may receive entropy encoded data for the currentblock, such as entropy encoded prediction information and entropyencoded data for transform coefficients of a residual blockcorresponding to the current block (370). Video decoder 300 may entropydecode the entropy encoded data to determine prediction information forthe current block and to reproduce transform coefficients of theresidual block (372). Video decoder 300 may predict the current block(374), e.g., using an intra- or inter-prediction mode as indicated bythe prediction information for the current block, to calculate aprediction block for the current block. Video decoder 300 may theninverse scan the reproduced transform coefficients (376), to create ablock of quantized transform coefficients. Video decoder 300 may theninverse quantize the transform coefficients and apply an inversetransform to the transform coefficients to produce a residual block(378). Video decoder 300 may ultimately decode the current block bycombining the prediction block and the residual block (380).

FIG. 9 is a flowchart illustrating an example process for decoding acurrent block of video data in accordance with the techniques of thisdisclosure. The current block may comprise a current CU. The techniquesof FIG. 9 will be described with respect to a generic video decoder. Thegeneric video decoder may, for example, corresponds to video decoder 300or another type of video decoder. The generic video decoder may alsocorrespond to the video decoding loop of a video encoder such, which mayfor example include mode selection unit 202, inverse quantization unit210, inverse transform processing unit 212, reconstruction unit 214,filter unit 216, and DPB 218 of video encoder 200.

In the example of FIG. 9 , the video decoder determines that a block iscoded in an overlapped block motion compensation (OBMC) mode (400). Thevideo decoder determines a first prediction block for the block using amotion vector of the block (402). The video decoder determines a secondprediction block for the block using a motion vector of a neighboringblock of the block (404).

The video decoder selects an OBMC blending process from a plurality ofavailable OBMC blending processes (406). To select the OBMC blendingprocess from the plurality of available OBMC blending processes, thevideo decoder may, for example, select weighting factors for blendingthe first prediction block and the second prediction block. To selectthe OBMC blending process from the plurality of available OBMC blendingprocesses, the video decoder may for example determine a number of rowsor columns of the first prediction block and the second prediction blockto be blended.

To select the OBMC blending process from the plurality of available OBMCblending processes, the video decoder may, for example, determine afirst cost for the first prediction block using a template matchingprocess; determine a second cost for the second prediction block usingthe template matching process; and select the OBMC blending process fromthe plurality of available OBMC blending processes based on the firstcost and the second cost. The video decoder may determine the first costfor the first prediction block using the template matching processcomprises comparing a template of the block to a template of the firstprediction block and determine the second cost for the second predictionblock using the template matching process comparing the template of theblock to a template of the second prediction block.

In response to a product of T and the first cost being less than orequal to the second cost, determining the blended block with a weightingof zero applied to the second prediction block. In response to a productof T and the first cost being greater than the second cost and the firstcost being less than or equal to the second cost, the video decoder mayselect as the OBMC blending process an OBMC blending process that blendstwo rows or columns. In response to a product of the second cost and Tbeing less than or equal to the first cost, the video decoder may selectas the OBMC blending process an OBMC blending process that blends fourrows or columns. In response to a product of T and the second cost beinggreater than the first cost and the second cost being less than or equalto the first cost, the video decoder may selecting as the OBMC blendingprocess an OBMC blending process that blends two rows or columns.

The video decoder determines a blended block based on the firstprediction block and the second prediction block, wherein determiningthe blended block based on the first prediction block and the secondprediction block comprises blending the first prediction block and thesecond prediction block using the selected OBMC blending process (408).

The video decoder reconstructs the block using the blended block (410).The video decoder may reconstruct the block by adding residual values tothe blended block. The video decoder may then perform one or morefiltering operations on the reconstructed block before outputting thedecoded block as part of a decode picture of video data. The videodecoder may, for example, output the decoded picture for immediatedisplay or store the decoded the picture for later transmission ordisplay. In scenarios where the video decoder is operating as part of avideo encoding process, the video decoder may store the decoded pictureto use when encoding subsequent pictures of video data.

The following numbered clauses illustrate one or more aspects of thedevices and techniques described in this disclosure.

Clause 1A: A method of decoding video data, the method comprising:determining that a block is coded in an overlapped block motioncompensation (OBMC) mode; selecting an OBMC blending process from aplurality of available OBMC blending processes; and decoding the blockusing the selected OBMC blending process.

Clause 2A: The method of clause 1A, wherein the plurality of availableOBMC blending processes comprises blending processes with differentweighting factors, different numbers of rows for blending, and/ordifferent numbers of columns for blending.

Clause 3A: The method of clause 1A or 2A, wherein selecting the OBMCblending process from the plurality of available OBMC blending processescomprises comparing a current template to a reference template.

Clause 4A: The method of any of clauses 1A-3A, wherein decoding theblock using the selected OBMC blending process comprises applying ablending filter.

Clause 5A: A device for coding video data, the device comprising one ormore means for performing the method of any of clauses 1A-4A.

Clause 6A: The device of clause 5A, wherein the one or more meanscomprise one or more processors implemented in circuitry.

Clause 7A: The device of any of clauses 5A and 6A, further comprising amemory to store the video data.

Clause 8A: The device of any of clauses 5A-7A, further comprising adisplay configured to display decoded video data.

Clause 9A: The device of any of clauses 5A-8A, wherein the devicecomprises one or more of a camera, a computer, a mobile device, abroadcast receiver device, or a set-top box.

Clause 10A: The device of any of clauses 5A-9A, wherein the devicecomprises a video decoder.

Clause 11A: The device of any of clauses 5A-10A, wherein the devicecomprises a video encoder.

Clause 12A: A computer-readable storage medium having stored thereoninstructions that, when executed, cause one or more processors toperform the method of any of clauses 1A-4A.

Clause 1B: A method of decoding video data, the method comprising:determining that a block is coded in an overlapped block motioncompensation (OBMC) mode; determining a first prediction block for theblock using a first motion vector for the block; determining a secondprediction block for the block using a second motion vector, wherein thesecond motion is a motion vector of a neighboring block of the block;selecting an OBMC blending process from a plurality of available OBMCblending processes; blending the first prediction block and the secondprediction block using the selected OBMC blending process to determine ablended block; and reconstructing the block using the blended block.

Clause 2B: The method of clause 1B, wherein selecting the OBMC blendingprocess from the plurality of available OBMC blending processescomprises selecting weighting factors for blending the first predictionblock and the second prediction block.

Clause 3B: The method of clause 1B, wherein selecting the OBMC blendingprocess from the plurality of available OBMC blending processescomprises determining a number of rows or columns of the firstprediction block and the second prediction block to be blended.

Clause 4B: The method of clause 1B, wherein selecting the OBMC blendingprocess from the plurality of available OBMC blending processescomprises: determining a first cost for the first prediction block usinga template matching process; determining a second cost for the secondprediction block using the template matching process; and selecting theOBMC blending process from the plurality of available OBMC blendingprocesses based on the first cost and the second cost.

Clause 5B: The method of clause 4B, wherein: determining the first costfor the first prediction block using the template matching processcomprises comparing a template of the block to a template of the firstprediction block; and determining the second cost for the secondprediction block using the template matching process comparing thetemplate of the block to a template of the second prediction block.

Clause 6B: The method of clause 4B, further comprising: in response to aproduct of T and the first cost being less than or equal to the secondcost, determining the blended block with a weighting of zero applied tothe second prediction block, wherein T comprises a positive valuegreater than 1.

Clause 7B: The method of clause 4B, further comprising: in response to aproduct of T and the first cost being greater than the second cost andthe first cost being less than or equal to the second cost, selecting asthe OBMC blending process, a first OBMC blending process that blends tworows or columns, wherein the plurality of available OBMC blendingprocesses includes the first OBMC blending process, a second OBMCblending process that blends four rows or columns, and a third OBMCblending process that blends zero rows or columns, wherein T comprises apositive value greater than 1.

Clause 8B: The method of clause 4B, further comprising: in response to aproduct of the second cost and T being less than or equal to the firstcost, selecting as the OBMC blending process, a first OBMC blendingprocess that blends four rows or columns, wherein the plurality ofavailable OBMC blending processes includes the first OBMC blendingprocess, a second OBMC blending process that blends less than four rowsor columns, and a third OBMC blending process that blends zero rows orcolumns, wherein T comprises a positive value greater than 1.

Clause 9B: The method of clause 4B, further comprising: in response to aproduct of T and the second cost being greater than the first cost andthe second cost being less than or equal to the first cost, selecting asthe OBMC blending process, a first OBMC blending process that blends tworows or columns, wherein the plurality of available OBMC blendingprocesses includes the first OBMC blending process, a second OBMCblending process that blends four rows or columns, and a third OBMCblending process that blends zero rows or columns, wherein T comprises apositive value greater than 1.

Clause 10B: A device for decoding encoded video data, the devicecomprising: a memory configured to store video data; one or moreprocessors implemented in circuitry and configured to: determine that ablock is coded in an overlapped block motion compensation (OBMC) mode;determine a first prediction block for the block using a first motionvector for the block; determine a second prediction block for the blockusing a second motion vector, wherein the second motion is a motionvector of a neighboring block of the block; select an OBMC blendingprocess from a plurality of available OBMC blending processes; blend thefirst prediction block and the second prediction block using theselected OBMC blending process to determine a blended block; andreconstruct the block using the blended block.

Clause 11B: The device of clause 10B, wherein to select the OBMCblending process from the plurality of available OBMC blendingprocesses, the one or more processors are further configured to selectweighting factors for blending the first prediction block and the secondprediction block.

Clause 12B: The device of clause 10B, wherein to select the OBMCblending process from the plurality of available OBMC blendingprocesses, the one or more processors are further configured todetermine a number of rows or columns of the first prediction block andthe second prediction block to be blended.

Clause 13B: The device of clause 10B, wherein to select the OBMCblending process from the plurality of available OBMC blendingprocesses, the one or more processors are further configured to:determine a first cost for the first prediction block using a templatematching process; determine a second cost for the second predictionblock using the template matching process; and select the OBMC blendingprocess from the plurality of available OBMC blending processes based onthe first cost and the second cost.

Clause 14B: The device of clause 13B, wherein: to determine the firstcost for the first prediction block using the template matching processcomprises, the one or more processors are further configured to comparea template of the block to a template of the first prediction block; andto determine the second cost for the second prediction block using thetemplate matching process, the one or more processors are furtherconfigured to compare the template of the block to a template of thesecond prediction block.

Clause 15B: The device of clause 14B, wherein the one or more processorsare further configured to: in response to a product of T and the firstcost being less than or equal to the second cost, determine the blendedblock with a weighting of zero applied to the second prediction block,wherein T comprises a positive value greater than 1.

Clause 16B: The device of clause 14B, wherein the one or more processorsare further configured to: in response to a product of T and the firstcost being greater than the second cost and the first cost being lessthan or equal to the second cost, select as the OBMC blending process, afirst OBMC blending process that blends two rows or columns, wherein theplurality of available OBMC blending processes includes the first OBMCblending process, a second OBMC blending process that blends four rowsor columns, and a third OBMC blending process that blends zero rows orcolumns, wherein T comprises a positive value greater than 1.

Clause 17B: The device of clause 14B, wherein the one or more processorsare further configured to: in response to a product of the second costand T being less than or equal to the first cost, select as the OBMCblending process, a first OBMC blending process that blends four rows orcolumns, wherein the plurality of available OBMC blending processesincludes the first OBMC blending process, a second OBMC blending processthat blends less than four rows or columns, and a third OBMC blendingprocess that blends zero rows or columns, wherein T comprises a positivevalue greater than 1.

Clause 18B: The device of clause 14B, wherein the one or more processorsare further configured to: in response to a product of T and the secondcost being greater than the first cost and the second cost being lessthan or equal to the first cost, select as the OBMC blending process, afirst OBMC blending process that blends two rows or columns, wherein theplurality of available OBMC blending processes includes the first OBMCblending process, a second OBMC blending process that blends four rowsor columns, and a third OBMC blending process that blends zero rows orcolumns, wherein T comprises a positive value greater than 1.

Clause 19B: The device of any of clauses 10B-18B, wherein the devicecomprises a wireless communication device, further comprising a receiverconfigured to receive the encoded video data.

Clause 20B: The device of clause 19B, wherein the wireless communicationdevice comprises a telephone handset and wherein the receiver isconfigured to demodulate, according to a wireless communicationstandard, a signal comprising the encoded video data.

Clause 21B: The device of any of clauses 10B-20B, further comprising: adisplay configured to display decoded video data.

Clause 22B: The device of any of clauses 10B-21B, wherein the devicecomprises one or more of a camera, a computer, a mobile device, abroadcast receiver device, or a set-top box.

Clause 23B: The device of any of clauses 10B-22B, wherein the devicecomprises a video encoding device.

Clause 24B: A computer-readable storage medium storing instructions thatwhen executed by one or more processors cause the one or more processorsto: determine that a block is coded in an overlapped block motioncompensation (OBMC) mode; determine a first prediction block for theblock using a first motion vector for the block; determine a secondprediction block for the block using a second motion vector, wherein thesecond motion is a motion vector of a neighboring block of the block;select an OBMC blending process from a plurality of available OBMCblending processes; blend the first prediction block and the secondprediction block using the selected OBMC blending process to determine ablended block; and reconstruct the block using the blended block.

Clause 25B: The computer-readable storage medium of clause 24B, whereinto select the OBMC blending process from the plurality of available OBMCblending processes, the one or more processors are further configured toselect weighting factors for blending the first prediction block and thesecond prediction block.

Clause 26B: The computer-readable storage medium of clause 24B, whereinto select the OBMC blending process from the plurality of available OBMCblending processes, the one or more processors are further configured todetermine a number of rows or columns of the first prediction block andthe second prediction block to be blended.

Clause 27B: The computer-readable storage medium of clause 24B, whereinto select the OBMC blending process from the plurality of available OBMCblending processes, the instructions cause the one or more processorsare further configured to: determine a first cost for the firstprediction block using a template matching process; determine a secondcost for the second prediction block using the template matchingprocess; and select the OBMC blending process from the plurality ofavailable OBMC blending processes based on the first cost and the secondcost.

Clause 28B: The computer-readable storage medium of clause 27B, wherein:to determine the first cost for the first prediction block using thetemplate matching process comprises, the instructions cause the one ormore processors are further configured to compare a template of theblock to a template of the first prediction block; and to determine thesecond cost for the second prediction block using the template matchingprocess, the instructions cause the one or more processors are furtherconfigured to compare the template of the block to a template of thesecond prediction block.

Clause 29B: The computer-readable storage medium of clause 27B, whereinthe instructions cause the one or more processors are further configuredto: in response to a product of T and the first cost being less than orequal to the second cost, determine the blended block with a weightingof zero applied to the second prediction block, wherein T comprises apositive value greater than 1.

Clause 30B: The computer-readable storage medium of clause 27B, whereinthe instructions cause the one or more processors are further configuredto: in response to a product of T and the first cost being greater thanthe second cost and the first cost being less than or equal to thesecond cost, select as the OBMC blending process, a first OBMC blendingprocess that blends two rows or columns, wherein the plurality ofavailable OBMC blending processes includes the first OBMC blendingprocess, a second OBMC blending process that blends four rows orcolumns, and a third OBMC blending process that blends zero rows orcolumns, wherein T comprises a positive value greater than 1.

Clause 31B: The computer-readable storage medium of clause 27B, whereinthe one or more processors are further configured to: in response to aproduct of the second cost and T being less than or equal to the firstcost, select as the OBMC blending process, a first OBMC blending processthat blends four rows or columns, wherein the plurality of availableOBMC blending processes includes the first OBMC blending process, asecond OBMC blending process that blends less than four rows or columns,and a third OBMC blending process that blends zero rows or columns,wherein T comprises a positive value greater than 1.

It is to be recognized that depending on the example, certain acts orevents of any of the techniques described herein can be performed in adifferent sequence, may be added, merged, or left out altogether (e.g.,not all described acts or events are necessary for the practice of thetechniques). Moreover, in certain examples, acts or events may beperformed concurrently, e.g., through multi-threaded processing,interrupt processing, or multiple processors, rather than sequentially.

In one or more examples, the functions described may be implemented inhardware, software, firmware, or any combination thereof. If implementedin software, the functions may be stored on or transmitted over as oneor more instructions or code on a computer-readable medium and executedby a hardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limitation, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore DSPs, general purpose microprocessors, ASICs, FPGAs, or otherequivalent integrated or discrete logic circuitry. Accordingly, theterms “processor” and “processing circuitry,” as used herein may referto any of the foregoing structures or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules configured for encoding anddecoding, or incorporated in a combined codec. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

Various examples have been described. These and other examples arewithin the scope of the following claims.

What is claimed is:
 1. A method of decoding video data, the methodcomprising: determining that a block is coded in an overlapped blockmotion compensation (OBMC) mode; determining a first prediction blockfor the block using a first motion vector for the block; determining asecond prediction block for the block using a second motion vector,wherein the second motion is a motion vector of a neighboring block ofthe block; selecting an OBMC blending process from a plurality ofavailable OBMC blending processes; blending the first prediction blockand the second prediction block using the selected OBMC blending processto determine a blended block; and reconstructing the block using theblended block.
 2. The method of claim 1, wherein selecting the OBMCblending process from the plurality of available OBMC blending processescomprises selecting weighting factors for blending the first predictionblock and the second prediction block.
 3. The method of claim 1, whereinselecting the OBMC blending process from the plurality of available OBMCblending processes comprises determining a number of rows or columns ofthe first prediction block and the second prediction block to beblended.
 4. The method of claim 1, wherein selecting the OBMC blendingprocess from the plurality of available OBMC blending processescomprises: determining a first cost for the first prediction block usinga template matching process; determining a second cost for the secondprediction block using the template matching process; and selecting theOBMC blending process from the plurality of available OBMC blendingprocesses based on the first cost and the second cost.
 5. The method ofclaim 4, wherein: determining the first cost for the first predictionblock using the template matching process comprises comparing a templateof the block to a template of the first prediction block; anddetermining the second cost for the second prediction block using thetemplate matching process comparing the template of the block to atemplate of the second prediction block.
 6. The method of claim 4,further comprising: in response to a product of T and the first costbeing less than or equal to the second cost, determining the blendedblock with a weighting of zero applied to the second prediction block,wherein T comprises a positive value greater than
 1. 7. The method ofclaim 4, further comprising: in response to a product of T and the firstcost being greater than the second cost and the first cost being lessthan or equal to the second cost, selecting as the OBMC blendingprocess, a first OBMC blending process that blends two rows or columns,wherein the plurality of available OBMC blending processes includes thefirst OBMC blending process, a second OBMC blending process that blendsfour rows or columns, and a third OBMC blending process that blends zerorows or columns, wherein T comprises a positive value greater than
 1. 8.The method of claim 4, further comprising: in response to a product ofthe second cost and T being less than or equal to the first cost,selecting as the OBMC blending process, a first OBMC blending processthat blends four rows or columns, wherein the plurality of availableOBMC blending processes includes the first OBMC blending process, asecond OBMC blending process that blends less than four rows or columns,and a third OBMC blending process that blends zero rows or columns,wherein T comprises a positive value greater than
 1. 9. The method ofclaim 4, further comprising: in response to a product of T and thesecond cost being greater than the first cost and the second cost beingless than or equal to the first cost, selecting as the OBMC blendingprocess, a first OBMC blending process that blends two rows or columns,wherein the plurality of available OBMC blending processes includes thefirst OBMC blending process, a second OBMC blending process that blendsfour rows or columns, and a third OBMC blending process that blends zerorows or columns, wherein T comprises a positive value greater than 1.10. A device for decoding encoded video data, the device comprising: amemory configured to store video data; one or more processorsimplemented in circuitry and configured to: determine that a block iscoded in an overlapped block motion compensation (OBMC) mode; determinea first prediction block for the block using a first motion vector forthe block; determine a second prediction block for the block using asecond motion vector, wherein the second motion is a motion vector of aneighboring block of the block; select an OBMC blending process from aplurality of available OBMC blending processes; blend the firstprediction block and the second prediction block using the selected OBMCblending process to determine a blended block; and reconstruct the blockusing the blended block.
 11. The device of claim 10, wherein to selectthe OBMC blending process from the plurality of available OBMC blendingprocesses, the one or more processors are further configured to selectweighting factors for blending the first prediction block and the secondprediction block.
 12. The device of claim 10, wherein to select the OBMCblending process from the plurality of available OBMC blendingprocesses, the one or more processors are further configured todetermine a number of rows or columns of the first prediction block andthe second prediction block to be blended.
 13. The device of claim 10,wherein to select the OBMC blending process from the plurality ofavailable OBMC blending processes, the one or more processors arefurther configured to: determine a first cost for the first predictionblock using a template matching process; determine a second cost for thesecond prediction block using the template matching process; and selectthe OBMC blending process from the plurality of available OBMC blendingprocesses based on the first cost and the second cost.
 14. The device ofclaim 13, wherein: to determine the first cost for the first predictionblock using the template matching process comprises, the one or moreprocessors are further configured to compare a template of the block toa template of the first prediction block; and to determine the secondcost for the second prediction block using the template matchingprocess, the one or more processors are further configured to comparethe template of the block to a template of the second prediction block.15. The device of claim 14, wherein the one or more processors arefurther configured to: in response to a product of T and the first costbeing less than or equal to the second cost, determine the blended blockwith a weighting of zero applied to the second prediction block, whereinT comprises a positive value greater than
 1. 16. The device of claim 14,wherein the one or more processors are further configured to: inresponse to a product of T and the first cost being greater than thesecond cost and the first cost being less than or equal to the secondcost, select as the OBMC blending process, a first OBMC blending processthat blends two rows or columns, wherein the plurality of available OBMCblending processes includes the first OBMC blending process, a secondOBMC blending process that blends four rows or columns, and a third OBMCblending process that blends zero rows or columns, wherein T comprises apositive value greater than
 1. 17. The device of claim 14, wherein theone or more processors are further configured to: in response to aproduct of the second cost and T being less than or equal to the firstcost, select as the OBMC blending process, a first OBMC blending processthat blends four rows or columns, wherein the plurality of availableOBMC blending processes includes the first OBMC blending process, asecond OBMC blending process that blends less than four rows or columns,and a third OBMC blending process that blends zero rows or columns,wherein T comprises a positive value greater than
 1. 18. The device ofclaim 14, wherein the one or more processors are further configured to:in response to a product of T and the second cost being greater than thefirst cost and the second cost being less than or equal to the firstcost, select as the OBMC blending process, a first OBMC blending processthat blends two rows or columns, wherein the plurality of available OBMCblending processes includes the first OBMC blending process, a secondOBMC blending process that blends four rows or columns, and a third OBMCblending process that blends zero rows or columns, wherein T comprises apositive value greater than
 1. 19. The device of claim 10, wherein thedevice comprises a wireless communication device, further comprising areceiver configured to receive the encoded video data.
 20. The device ofclaim 19, wherein the wireless communication device comprises atelephone handset and wherein the receiver is configured to demodulate,according to a wireless communication standard, a signal comprising theencoded video data.
 21. The device of claim 10, further comprising: adisplay configured to display decoded video data.
 22. The device ofclaim 10, wherein the device comprises one or more of a camera, acomputer, a mobile device, a broadcast receiver device, or a set-topbox.
 23. The device of claim 10, wherein the device comprises a videoencoding device.
 24. A computer-readable storage medium storinginstructions that when executed by one or more processors cause the oneor more processors to: determine that a block is coded in an overlappedblock motion compensation (OBMC) mode; determine a first predictionblock for the block using a first motion vector for the block; determinea second prediction block for the block using a second motion vector,wherein the second motion is a motion vector of a neighboring block ofthe block; select an OBMC blending process from a plurality of availableOBMC blending processes; blend the first prediction block and the secondprediction block using the selected OBMC blending process to determine ablended block; and reconstruct the block using the blended block. 25.The computer-readable storage medium of claim 24, wherein to select theOBMC blending process from the plurality of available OBMC blendingprocesses, the one or more processors are further configured to selectweighting factors for blending the first prediction block and the secondprediction block.
 26. The computer-readable storage medium of claim 24,wherein to select the OBMC blending process from the plurality ofavailable OBMC blending processes, the one or more processors arefurther configured to determine a number of rows or columns of the firstprediction block and the second prediction block to be blended.
 27. Thecomputer-readable storage medium of claim 24, wherein to select the OBMCblending process from the plurality of available OBMC blendingprocesses, the instructions cause the one or more processors are furtherconfigured to: determine a first cost for the first prediction blockusing a template matching process; determine a second cost for thesecond prediction block using the template matching process; and selectthe OBMC blending process from the plurality of available OBMC blendingprocesses based on the first cost and the second cost.
 28. Thecomputer-readable storage medium of claim 27, wherein: to determine thefirst cost for the first prediction block using the template matchingprocess comprises, the instructions cause the one or more processors arefurther configured to compare a template of the block to a template ofthe first prediction block; and to determine the second cost for thesecond prediction block using the template matching process, theinstructions cause the one or more processors are further configured tocompare the template of the block to a template of the second predictionblock.
 29. The computer-readable storage medium of claim 27, wherein theinstructions cause the one or more processors are further configured to:in response to a product of T and the first cost being less than orequal to the second cost, determine the blended block with a weightingof zero applied to the second prediction block, wherein T comprises apositive value greater than
 1. 30. The computer-readable storage mediumof claim 27, wherein the instructions cause the one or more processorsare further configured to: in response to a product of T and the firstcost being greater than the second cost and the first cost being lessthan or equal to the second cost, select as the OBMC blending process, afirst OBMC blending process that blends two rows or columns, wherein theplurality of available OBMC blending processes includes the first OBMCblending process, a second OBMC blending process that blends four rowsor columns, and a third OBMC blending process that blends zero rows orcolumns, wherein T comprises a positive value greater than
 1. 31. Thecomputer-readable storage medium of claim 27, wherein the one or moreprocessors are further configured to: in response to a product of thesecond cost and T being less than or equal to the first cost, select asthe OBMC blending process, a first OBMC blending process that blendsfour rows or columns, wherein the plurality of available OBMC blendingprocesses includes the first OBMC blending process, a second OBMCblending process that blends less than four rows or columns, and a thirdOBMC blending process that blends zero rows or columns, wherein Tcomprises a positive value greater than 1.